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Forage quality counts

Mike Hutjens for Progressive Dairy Published on 22 May 2020

Looking back to the 2019 forage year, it was a disaster for some dairy farms and a challenge for most. It was almost a perfect storm; several factors that could go wrong happened somewhere.

  • Winterkill of alfalfa and winter wheat reduced forage acreage.

  • Early spring rain prevented planting of corn and small grains.

  • First cutting was delayed due to rain, or fields could not allow heavy equipment without causing field damage.

  • Dry weather in July and August reduced cuttings.

  • Corn silage planted in June did not reach maturity until late fall.

  • Heavy fall rain and early snow prevented chopping corn silage.

As a result, milk yields were negatively impacted along with reduced forage yields and inventory needs. Forage quality factors are discussed below.

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Factors affecting forage quality

Forage quality on dairy farms changes every year due to factors that cannot be controlled by the dairy management team, while other factors can be modified on the farm. A partial list is outlined below.

  • Growing conditions including sunlight (favorable for photosynthesis), temperature (favorable for growth) and water (required for plant growth; a shortage causes drought stress, and excess water can damage the plant.) Dairy farmers have little control unless irrigating.

  • Leaf-to-stem ratio is important for legumes and grasses as leaf dry matter contains higher nutrient value while stems are lower in digestibility due to lignification. Dairy farmers have some control when selecting hybrids and harvesting at optimal maturity.

  • Grain-to-stalk ratio is important for corn silage. Grain contains high energy value due to starch content. Grain stalk is lower in feed value and can limit feed intake. Dairy farmers have some control when selecting hybrids and cutting height.

  • Stage of maturity dictates forage digestibility, nutrient content and dry matter yield. In most cases, these factors change in opposing directions. (As maturity increases, yield goes up while nutrient levels are declining.) Weather can delay harvest plans. Low-lignin forages may expand the harvest window. Dairy farmers have control when harvesting the forage crop, weather permitting, and hybrid selection.

  • Harvest losses can be significant as leaf loss, poor fermentation due to soil, mycotoxin and yeast development, weather damage after cutting in the field, losses due to dry matter content of harvested crop and harvest system losses. (Merging forage, baling, chopping, wrapping and outside storage are examples.) Dairy farmers have control with weather risks.

  • Soil fertility has significant impacts on forage quality and yield. Rich soil results in forage improvements. Dairy farmers can modify soil fertility by application of manure and organic matter, strategic use and placement of fertilizer, and applying lime to adjust soil pH. Dairy farmers have control.

Defining forage quality

Evaluating forage quality will depend on the forage crop. Nutritionists and dairy farmers may consider different factors defining forage quality. Dairy animals (high-producing cows versus dry cows versus heifers) have different nutrient and dry matter intake requirements that can allow for strategic use of forage quality on the dairy farm.

Legume and grass quality could use the following test results: crude protein (CP), soluble protein, neutral detergent fiber (NDF), NDFD (digestibility of the NDF), lignin, uNDF and relative forage quality (RFQ). Table 1 has NDFD values. High-producing cows should be fed RFQ values over 150 while lower-producing cows, dry cows and older heifers can meet nutrient needs at RFQ values below 150.

NDFD 48-hour summary

Corn silage quality indexes could include starch level, NDF, NDFD, uNDF and CP. NDFD is my first value I consider, as it provides an index of digestible and available energy. Crude protein is expensive to purchase, but the dairy cow must capture soluble protein as microbial protein. The use of uNDF can be used to determine feed intake and rate of passage indirectly. Table 1 lists typical NDFD-48 hours with range values. No lower-lignin forages are included in Table 1.

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Strategies related to forage quality

Forage particles over 2 inches in length risk sorting against these forage particles related to stem quality and slows feed consumption. Dairy cows reduce the feed particle length down to 10 millimeters (about a half-inch) by chewing before swallowing. The additional chewing time can increase saliva production and buffering but can reduce and slow feed intake. When using the Penn State Particle Box, target less than 10% in the top box when evaluating forages with no forage particles over 1 inch in length. The second box from the top (holes are 0.3-inch diameter) should be over 55%.

Based on research at the Miner Institute in Chazy, New York, lower-quality grass and legume forage can be processed shorter to improve feed intake and performance. High-quality forage should be processed longer to optimize rate of passage and rumen fermentation.

Extending storage of corn silage increases the fermentation and availability of corn grain starch. Starch availability increases from harvest to three to four months after storage as the protein matrix that “locks up” starch granules are degraded. This change in starch has been termed “holiday corn silage” (harvested in the fall of 2019 and waiting until 2020 to feed the fermented corn silage).

Lower-lignin-content forages are available for corn silage, alfalfa, sorghum and sorghum-sudan hybrids. Lower-lignin forages provide an opportunity to improve forage quality, intake and nutrient content while allowing flexibility in your harvest system. Additional management factors should be considered including seed costs, standability and/or fungicide needs.

Forage extenders

When on-farm forage traditional sources are limiting, feed ingredients that contain fiber can be added to stretch available forages. Fiber can be defined as chemical fiber (such as 30% NDF) and physical fiber (contributes to the forage mat in the rumen and slow down rate of passage). For example, soyhulls contain xx percent chemical fiber but little physical fiber, especially if soyhulls are ground and pelleted. Fuzzy whole cottonseed contains xx percent NDF with 75% of the fiber as effective fiber. It is important to extend available forages on the farm before running out. Five pounds of a forage extender byproduct feed can fit as long as traditional forage fiber remains in the diet. The source of forage extenders vary on location and cost (beet pulp, corn gluten feed, soyhulls, wheat midds, citrus pulp or almond hulls).

Lessons learned in 2019

With over 20 million acres of prevented plants acreage in 2019, dairy farmers made important decisions and changes. Forages from prevented plant acres could be harvested after Sept. 1, 2019. The following strategies were considered:

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  • Corn silage planted in June reached corn silage maturity in late fall due to warm growing conditions. Shorter-maturity hybrids allow for improved grain development. Corn silage was the “go to” crop to achieve higher dry matter yields per acre.

  • Higher corn plant populations (over 80,000 seeds per acre) were planted in June in prevented plant acreage. While no grain could be harvested, this approach resulted in higher dry matter recovery and similar to a grass forage.

  • Planting sorghum-sudangrass hybrids in May in winterkill acreage resulted in harvesting every 30 days in forage quality, meeting the nutrient needs of high-producing cows. These forages were harvested at 24 to 30 inches in height. If dry cow and heifer forage inventories were needed, delaying harvest to allow growth to 40 to 50 inches increased dry matter yield. Manure applied after each cutting increased regrowth due to the added soil nutrients. If the crop served as a cover crop on prevented plant acres, strategic cutting in July and August allowed for the desired forage quality after Sept. 1.

  • Fall oats planted in August provided high-quality haylage 60 days after planting, depending on fall moisture and temperatures.  end mark
Mike Hutjens
  • Mike Hutjens

  • Professor of Animal Sciences Emeritus
  • University of Illinois – Urbana

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